Combined Effects of Teleconnection Patterns on Anomalous Summer Weather in Japan
Combined Effects of Teleconnection Patterns on Anomalous Summer Weather in Japan
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DOI：
10.2151/jmsj.85.11
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发表时间：
2007-02
影响因子：
3.1
通讯作者：
Takuya Ogasawara;R. Kawamura
中科院分区：
文献类型：
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作者：
Takuya Ogasawara;R. Kawamura
利用ERA-40和NCEP/NCAR再分析资料，分析了主要遥相关型，特别是西亚-日本(WJ)和太平洋-日本(PJ)型，其中高频(HF)分量(半周至2~3周)和低频(LF)分量(大于1个月)的特征，讨论了这些遥相关型对日本及周边地区夏季异常天气的综合影响。HF-WJ型与亚洲夏季风活动关系不密切，而LF-WJ型与夏季风区异常季风加热显著相关。与菲律宾海强对流激发的驻波相一致的HF-PJ和LF-PJ模式，在日本以东产生了一个近乎正压的反气旋异常。HF-WJ和HF-PJ模式的组合在日本北部建立了一个纬向拉长的反气旋异常，导致日本北部地表温度异常高。这种耦合导致该地区的增温大于单独的遥相关型。典型的LF-WJ和LF-PJ组合也表明日本北部存在纬向拉长的反气旋异常，这与HF-WJ和HF-PJ的组合模式相似。LFWJ对日本周围地面温度场的动态影响与LFPJ有明显不同。低频西风的主导作用导致日本上空下沉增强，从而导致绝热加热和入射太阳辐射增加。另一方面，PJ引起的对流层低层反气旋异常有利于北向暖平流到南北温度梯度较大的日本北部以东。至于2004年的酷热夏季，没有发现低频-WJ和LF-PJ的组合型。另外，在6月中旬，低层位势高度场出现了三极结构。这种三极子模式可能是由LF-PJ和从高纬度向东南传播的正压Rossby波列的组合建立的。
Using ERA-40 and NCEP/NCAR reanalysis data, the characteristics of major teleconnection patterns were examined, particularly the West Asia-Japan (WJ) and Pacific-Japan (PJ) patterns, with a high-frequency (HF) component (from half a week to two or three weeks), and a low-frequency (LF) component (greater than about one month), and discussed the combined effects of the teleconnection patterns on the anomalous summer weather in Japan and the surrounding regions.Both patterns of the HF-WJ and LF-WJ, which propagate eastward along the upper-level Asian jet, induce an anomalous barotropic anticyclone centered on the Japan Sea. The HF-WJ pattern has no close link with the Asian summer monsoon activity, but, in contrast, the LF-WJ pattern is significantly correlated with anomalous monsoonal heating over the summer monsoon region. The HF-PJ and LF-PJ patterns, which can be identified with stationary waves stimulated by intense convection around the Philippine Sea, generate a nearly barotropic anticyclone anomaly to the east of Japan. A combination of the HF-WJ and HF-PJ patterns establishes a zonally elongated anticyclonic anomaly over northern Japan, resulting in anomalous high surface temperatures in northern Japan. Such a coupling was found to lead to a larger temperature increase in that region than a single teleconnection pattern alone.A typical case of the LF-WJ and LF-PJ combination also indicates a zonally elongated anticyclonic anomaly over northern Japan, which is similar to the combined pattern of HF-WJ and HF-PJ. The dynamic impact of LF-WJ on the surface temperature field around Japan differs significantly from that of LF-PJ. The dominance of the LF-WJ causes enhanced subsidence over Japan, which can bring about adiabatic heating and increased incoming solar radiation. On the other hand, PJ-induced anomalous anticyclone in the lower troposphere facilitates northward warm advection to the east of northern Japan, where the north-south temperature gradient is large. As for the extreme hot summer of 2004, no combined patterns of the LF-WJ and LF-PJ were found during the summer. Alternatively, a tripole structure appeared in the lower geopotential height field in mid-June. Such a tripole pattern may be established by a combination of the LF-PJ and a barotropic Rossby wave train propagating southeastward from high latitudes.